Miniature high-voltage power supplies

ABSTRACT

The present invention provides a system comprising a high-voltage capacitive device and a power circuit electrically coupled to the capacitive device, wherein the power circuit is configured for stepping up a lower DC source voltage to a higher DC output voltage, wherein the source voltage is less than about 5 V, and wherein the output voltage is at least about 1.25 kV, and wherein the power circuit comprises a magnetic component and a switching component for charging and discharging the magnetic component, wherein the switching component has a high resistance of at least about 5 ohms.

FIELD OF THE INVENTION

The present invention is related to very compact, low-power,high-voltage power supplies.

BACKGROUND

High-voltage power supplies are commonly used and well-known forpowering devices which require a high DC voltage. Most high-voltagepower supplies include a transformer or inductor for converting orstepping-up a relatively low DC source voltage to a relatively high DCoutput voltage. Components, such as the transformer or inductor, diodes,and capacitors used in high-voltage power supply circuits must be ableto withstand the effects of high voltages and, thus, are oftenrelatively large and heavy. In smaller and/or portable devicesnecessitating the use of a low DC voltage source, i.e., a batterysupplying 5V or less, use of such large/heavy power components isprohibitive. Even where power supply size is not as much of an issue,where the high-voltage device being powered is mostly capacitive innature, efficiently modulating the voltage across the capacitive devicecan be problematic. This is particularly the ease with high-frequency(up to 10 kHz or more) capacitive devices, e.g., high-speed actuators,electronic displays, etc.

There are commonly known power circuit topologies which can be used inlieu of larger power components and also address the problem of highvoltage modulation. One such topology approach is the cascading (seriesconnection) of multiple transistor switch devices to reach a desiredvoltage rating. However, a significant number of parts must be added (asmany as ten or more cascaded switch multipliers may be required) inaddition to the main power devices, possibly including high voltagedrive transformers with difficult isolation requirements. An additionalconcern for the modulation of high voltages in capacitive devices isthat of power dissipation due to parasitic capacitances across theswitching devices. In a fast switching circuit, this energy isdissipated in the transistor switch at every turn-on, and can result ina substantial amount of power dissipation. Power dissipation isparticularly acute in high voltage circuits where losses due tohigh-frequency switching activity (commonly referred to as “switchingloss”) can quickly reach unacceptable levels. In addition to reducingefficiency, these losses can increase the temperature of the switchingelements beyond their ratings, causing premature failure.

Converter topologies such as zero voltage switching (ZVS) and zerocurrent switching (ZCS) address the problem of power dissipation due toswitching loss; however, they have complex designs with a high partcount, which adds to the size and cost of the power supply.

A boost converter is another type of high voltage power circuit topologywhich provides voltage gains in the range from about 20× to 50×. Theyare advantageous in that they are relatively small and compact; however,conventional boost converters do not fully address the problem of powerdissipation due to switching losses. Additionally, because they employhigh-impedance switching circuits, they are also subject to conductionlosses. In order to obviate the conductive losses, additional circuitryis commonly incorporated, but at the sake of increasing the overall sizeand weight of the power supply.

Another common approach is to use larger switching devices that havesignificantly lower conduction losses, i.e., lower on-state resistance.This increases the size and cost of the power supply. Even where thehigh-voltage device being powered requires a relatively low supplyvoltage, i.e., less than about 2 kV, the components of conventionalboost converters do not allow for much of a corresponding reduction inpower supply size due to the additional circuitry required to mitigatethe conductive losses. Nonetheless, boost circuits have been regarded asan optimal way in which to provide DC-DC voltage step-up. This isespecially true for supplies where the ratio of output voltage to inputvoltage exceeds a factor of one hundred or more.

Other types of power circuit topologies are well-known and commonly-usedto reduce the power dissipation which occurs through switching losswithout greatly adding to the weight, size or mass of the power supply.One such circuit topology is a multi-stage voltage multiplier circuitwhich is coupled to the output side of the transformer or inductor.Another topology includes a flyback circuit. These circuits minimizeconductive losses as they involve switches having very low resistance.While these circuit topologies reduce power dissipation and are notprohibitively large or heavy for use with smaller high-voltage devices,they are still too large and heavy to be provided in a form fit toaccommodate miniature device applications, such as cell phone cameramodules, camera flashes, etc.

Another approach to high voltage modulation involves coupling thetransducer directly to a transformer. The transformer approach allowsthe high transducer voltage to be stepped down by the transformer turnsratio such that charging and discharging can be accomplished at lowvoltages. However, the size of the required transformer increases as thefrequency of the charge/discharge cycle decreases. Thus, for themajority of applications in which weight, size and mass considerationsare essential, the required transformer is unacceptably large.

One approach to reducing the size of the transformer or inductor (i.e.,the magnetic components, generally) and, thus, the overall size andweight of the power supply in high-voltage applications, has been to useswitching components having very high switching frequencies, i.e., inthe range from about 200 kHz to 2 MHz. Of course, this approach presentsthe problem of power dissipation due to switching losses discussedabove.

Notwithstanding the operational shortcomings of prior art powersupplies, there are certain conventional power circuit topologies whichenable relatively small power supply architectures. Examples ofcommercially available “miniature” DC-DC converters which employ one ormore of the above approaches are as follows: EMCO High VoltageCorporation Q Series (Q50-5) converter supplying up to 5 kV output withan architecture having a volume of 0.125 in³ (approximately 2.050 mm³)and weighing 0.15 ounces (4.25 g); Gamma High Voltage Research, Inc. SMSeries power supply supplying up to 3 kV and having an architecturevolume of less than 1 in³ (approximately 16,400 mm³); MatsusadaPrecision, Inc. UP Series power supply with outputs from 100 to 500 Vand having an architecture volume of 0.432 in³ (approximately 7,080 mm³)and AM Power Systems high voltage converters with outputs from 500 V to5 kV and having an architecture volume of about 1 in³ (approximately16,400 mm³) and weighing about 1 ounce (29 grams). While the sizes ofthese “miniature” power supplies are relatively small, the inventorshereof are not aware of an available power supply having an even smallerarchitecture, or one that could be scaled-down in size even with asubstantially lower output voltage requirement, e.g., less than 2 kV.

In sum, prior art high-voltage power supply technology involves atradeoff between size/weight and power dissipation due to switchinglosses. Thus, there continues to be an interest and need in developinghigh-voltage power supplies where size and weight efficiency isparamount without sacrificing power efficiency. As such, it would behighly beneficial to provide a high-voltage power supply made ofextremely cost-effective, light-weight components which can realizeultra-miniature power supply architectures without the expectedswitching losses. Further, it would be highly advantageous to providesuch a power circuitry topology which gives a manufacturer theflexibility in scaling the size of the power supply to the desiredvoltage output of the supply.

SUMMARY OF THE INVENTION

The present invention includes novel circuitry for powering devicesrequiring a high-voltage supply. The power circuitry of the presentinvention provides a novel circuit topology which utilizes extremelysmall and light-weight components which enable an ultra-miniature powersupply architecture and which also minimize power dissipation due toswitching losses. In particular, the novel power topology compriseshigh-resistance switching components. This is opposite to the approachtaken with most power circuits of the prior art which employlow-resistance switches in order to minimize switching losses.Additionally, the switching components of the inventive circuitry aredesigned to operate at frequencies which are much lower than prior artpower circuits without compromising the size of the circuit's magneticcomponents, i.e., inductor/transformer. This novel circuitry providessome unpredictable advantages which are explained in greater detailbelow.

In one variation, the subject power circuitry is configured to power ahigh-voltage capacitive load. In one embodiment thereof, the capacitiveload is a very thin polymer film capacitor and, more particularly, is atransducer comprising a dielectric elastomer, also referred to as“electroactive polymer” (EAP). In a further embodiment, the EAPtransducer is configured for positioning a miniature lens for use in avery small camera device, such as cell phone camera.

The present invention also provides power supplies comprising thesubject power circuitry where the components thereof are relativelysmall and arranged in such a manner to reduce the number and size of thenecessary components, thus reducing the overall space requirements andtotal cost of the power supply. Moreover, the subject power circuittopology provides a manufacturer with the flexibility of scaling thesize of the power supply to the desired voltage output of the supply.More specifically, the subject topology allows sealing of the powersupply size as power output requirements are lowered.

The present invention also includes methods for powering devicesrequiring a high-voltage supply, where the methods may be performedusing the power circuitry or power supplies of the present invention.One such method involves charging and discharging the magnetic componentof the power circuitry at a relatively high frequency.

While the subject circuits and methods may be employed with anyhigh-voltage application, they are particularly suited forultra-miniature devices.

These and other features, objects and advantages of the invention willbecome apparent to those persons skilled in the art upon reading thedetails of the invention as more fully described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is best understood from the following detailed descriptionwhen read in conjunction with the accompanying schematic drawings. Tofacilitate understanding, the same reference numerals have been used(where practical) to designate similar elements that are common to thedrawings. Included in the drawings are the following:

FIG. 1 is a block diagram and schematic representation of a power supplycircuit of the present invention; and

FIG. 2 is a perspective view of a power supply of the present inventionhaving an ultra-miniature architecture; and

FIGS. 3A-3D are top perspective, bottom perspective, top and side views,respectively, of a camera lens module having the power supply of FIG. 2integrated therewith.

Variation of the invention from that shown in the figures iscontemplated.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides power circuitry and power supplies foruse in powering high-voltage devices where the available input voltageis relatively low and is required to be “stepped up” to a relativelyhigh voltage to adequately power the device. While the subject inventionmay be employed with any high-voltage device, the invention isparticularly described in the context of a device which provides acapacitive load. Still yet, for purposes of illustration only, thecapacitive load used in the context of this description is a dielectricelastomer/electroactive polymer transducer, which is described ingreater detail below.

A general configuration of a power supply 10 of the present invention isprovided in the block diagram of FIG. 1. In general, power supply 10includes power circuit 12 and voltage multiplier circuit 14. Powercircuit 12 has an input 18 coupled to a relatively low DC source signalV_(S) (e.g., 2 to 5 volt range) and an output coupled to the input sideof voltage multiplier circuit 14. Circuit 12, which functions similarlyto a boost-type circuit, converts the DC source signal to a pulsedsingle-polarity signal V₁ having a very narrow pulse width whileproviding a voltage gain of greater than about 100×, and even as greatas 250×, while still minimizing the overall power supply size, as isdiscussed in greater detail below. Of course, greater gains can berealized but with marginally larger architectures. Multiplier circuit14, in turn, converts this pulsed voltage signal V₁ to a “stepped up” DCvoltage output V_(O) which is substantially proportional (multiplied bythe number of stages) to the input voltage V₁. The number of “stages”employed by a multiplier circuit is selected to provide the desiredoutput signal V_(O). In the illustrated example, multiplier circuit 14has two stages, often referred to as a “voltage-doubler.” Output voltageV_(O1) is used to power a high-voltage device—here represented as acapacitive load 16.

In another variation of the present invention, the power supply does notinclude a multiplier circuit, with a single-stage, stepped-up DC voltageoutput (at V_(O2)) provided solely by power circuit 12. Power circuit 12(with or without the elimination of capacitor C2) by itself can be anefficient charger for capacitive loads because the current-voltageoutput of power circuit 12 can match the charge state of a capacitiveload better than many other types of charging circuits (i.e., at theonset of charging the load, it is desirable to charge it with relativelylow voltage and high current, as compared to the nearly fully-chargedstate when the voltage is relatively high at a lower current). Ofcourse, if a higher voltage output is required, any number of multiplierstages may also be used.

Power circuit 12 comprises inductor L1, transistor Q1, diode D1,capacitors C1 and C2, timing circuit comprised of oscillator U1 andresistor R1. A transformer may be employed as the magnetic component inlieu of the inductor if isolation between the circuit input and outputis required or desired. For purposes of describing the operation ofcircuit 12, steady-state operation is assumed. The onset of conductionin switching transistor Q1 is caused by raising the gate-source voltage(i.e., across terminals G and S) at the beginning of a switching period.With transistor Q1 “on”, the source voltage V_(S) is applied acrossinductor L1. The orientation of diode D1 is such that diode D1 cannotconduct current while transistor Q1 is on. Transistor Q1 remains on fora period of time set by oscillator U1 and resistor R1, whichcollectively define the switching frequency of the transistor. At theend of this time period, the gate-source voltage of transistor Q1 isreturned to zero, and transistor Q1 ceases to conduct current. Whentransistor Q1 is turned off, the voltage across inductor L1 rises,scaled up by the energy stored in the inductor. When the inductorvoltage slightly exceeds the first stage voltage V_(O2), diode D1 beginsto conduct, enabling current to flow to the output and therebytransferring energy (V₁) previously stored in inductor L1 to thecapacitor C2. Where no multiplier circuit is employed (and wherecapacitor C2 is eliminated from the power circuit when a capacitive loadis being powered), this voltage (V_(O2)) is outputted to load 16 a(shown in phantom). Meanwhile, in either case, diode D1 prevents thecurrent from reversing direction. Thus, as energy is transferred to theoutput capacitor C2, or directly to load 16 a in the latterconfiguration, the inductor L1 current decreases. When transistor Q1turns on again, the process is repeated.

Multiplier circuit 14 is a voltage doubler, i.e., provides two stages,where capacitor C2 and diode D1 (of power circuit 12) collectivelydefine the first stage, capacitor C3 and diode D2 collectively definethe transfer stage and capacitor C4 and diode D3 collectively define thesecond stage. Resistor R2 is used to discharge (capacitive) load 16. Themagnitude of V_(O1) is obtained by adding the voltages across the twostages of circuit 14, i.e., 2X where X is the value of the magnitude ofV₁.

The respective values of the capacitors, diodes and resistors of thepower and multiplier circuits are primarily selected based on outputvoltage (V_(O)) requirements, and input voltage (V₁) and source voltage(V_(S)) magnitude, as well as component cost and size constraints.Selection of the capacitance values may also be based on AC signalfrequency and magnitude. Additionally, the switching speed, andparticularly the reverse recovery time, of all of the diodes in thecircuit, especially diode D1, is preferably as fast as possible, i.e.,typically less than 50 ns, due to the narrow pulse width of voltagesignal V₁—otherwise some of the pulse voltage may be lost with a lowerresulting output voltage and reduced efficiency.

One aspect of the power circuit 12 of the present invention whichdiffers from conventional power supply circuits is the resistivity ofthe circuit. As discussed above, conventional step-up converter circuitsare used in high-voltage power supplies for their low resistance inorder to minimize the switching losses undergone by the power supply dueto the conduction losses of the switching transistor. As such, theswitching transistor used in conventional converter circuits is usuallya MOSFET having a relatively low resistance rating (i.e., typically lessthan 1 ohm). Power circuit 12 of the present invention, instead, employsa transistor Q1 which has a much higher resistance rating (i.e., atleast about 5 ohms and more typically in the range from about 10 toabout 30 ohms). Here, transistor Q1 is depicted as a MOSFET but may beany high-resistance switch device (e.g., a BJT, IGBT, and other similarcomponents, etc.). While this topology does not minimize conductivelosses, the associated stray capacitance of the switch is significantlylower. This significantly lower stray capacitance (typically about 3-4picofarads) allows a very high voltage gain across inductor L1 when Q1switches off. Typical capacitance of lower resistance switches of theprior art can be as high as 100 picofarads, which can significantlyaffect the maximum voltage gain obtainable from an inductor.

Another feature of the power circuit 12 of the present invention whichdiffers from conventional power supply circuits is the relatively lowswitching frequency of the circuit. As discussed above, conventionalstep-up converter circuits are used in high-voltage power supplies fortheir high switching frequencies (i.e., 200 kHz to 2 MHz) in order toreduce the size of the magnetic components, i.e., the inductor ortransformer. Conversely, power circuit 12 of the present inventionemploys a transistor Q1 which is being operated at a much lowerswitching frequency (i.e., less than about 30 kHz, and even lower thanabout 20 kHz).

Each of the circuit/component features of the subject power supplieswhich has been discussed herein individually contributes to a reducedform-fit, whether in volume, mass and/or weight. Their integration andcollective use, however, enables a further reduction in power supplysize where this additional size-reduction is non-linear, i.e., the sizeof the whole is less the size of the sum of the individual componentsthat would be expected using other circuit topologies. For example, thehigh-resistance “boost” circuit of the present invention (which allowsfor sufficient step-up voltage production in the inductor without theswitching losses experienced by prior art boost circuits) does notrequire the additional stages in the multiplier circuit (if at all) thatwould otherwise be necessary with a low-resistance boost circuit havinggreater stray capacitance across the switch. Fewer multiplier stagesmean fewer components which, in turn, reduce the size, weight and costof the power supply. The subject power supplies have structures that,depending on the output voltage requirements of the application at hand,may have volumes less than about 2000 mm³, and more typically less thanabout 1000 mm³, and even less than about 300 mm³, and weigh less thanabout 4 g, and more typically less than about 1 g, and even less thanabout 500 mg.

FIG. 2 illustrates one exemplary architecture in which the subject powersupplies may be provided. With the minimal number of necessarycomponents (with minimal size and weight) used to construct the subjectcircuitry, a power supply of the present invention may be providedwithin a flex circuit assembly 20, which includes a flex circuit 22 uponwhich the power components 24 a, 24 b, 24 c are mounted. The powercomponents may be integrated info one or more “potted” circuits 24 a, 24b (e.g., a boost converter circuit and a multiplier circuit,respectively) for fixation to circuit 22. Other discrete components,such as inductor 24 c, may also be mounted to the flex circuit. Flexcircuit 22 may also be configured with conductive leads 26 a, 26 b orconnectors 28 for electrical coupling to the high voltage and groundsides of the device to be powered and to the DC source voltage,respectively. As its name implies, flex circuit 22 is flexible and maybe bent or shaped into a selected form fit to accommodate, e.g.,contact, wrap around, encase, etc., the device (now shown) being poweredin a contoured or flush manner so as to minimize space requirements. Forexample, here flex circuit 22 is provided in a narrow rectangularconfiguration and has been bent crosswise 22 a to its length to form asubstantially right angle to accommodate, for example, a corner of adevice (not shown) which it is to power.

The actual size and weight of the subject power supplies depend onvarious factors, including the magnitude of the source voltage and thenecessary voltage step-up required to power the high-voltage device,which may affect the size of the individual components discussed above.For example with a voltage input (i.e., a source voltage) of 0 to about5V and an output voltage of about 1.25 kV, the necessary size of thepower supply components employed may yield a power supply architecturehaving the following exemplary dimensions: with reference to FIG. 2,length dimensions (D₁ and D₂) less than about 10 mm, width dimensions(D3) less than about 2.5 mm, and height dimensions less than about 5 mm.Of course, the total volume occupied by the power supply is in partdependent on how compact assembly 20 is made to be, i.e., by wrapping orfolding of the flex circuit to a minimal profile. With the dimensionsprovided, power supply architecture volumes of less than about 250 mm³(10 mm×2.5 mm×5 mm×2) may be realized. Further, the subject powersupplies may be designed to weigh less than about 330 mg. Of course,even smaller sizes and weights may be realized for power supplies havinglower input and output voltages requirements as smaller and lighterswitching and magnetic components of the power supply may be employed.In this way, the power circuitry of the present invention enables powersupply manufacturers to somewhat proportionately scale the size andweight of the supply to the necessary voltage requirements.

The subject power supplies are well-suited for powering high-voltagecapacitive loads which themselves employ a miniature architecture. Inone variation, the subject power supplies are particularly configured topower High-voltage devices employing an EAP transducer. Because of theirlight weight and few components, EAP transducers offer a very lowprofile and are ideal for use in very small scale applications.Generally, these transducers comprise two thin film electrodes havingelastic characteristics and separated by a thin elastomeric dielectricpolymer (e.g., made of acrylic, silicone, or the like). When a voltagedifference is applied across the oppositely-charged electrodes, theelectrodes attract each other thereby compressing the polymer dielectriclayer therebetween. As the electrodes are pulled closer together, thedielectric polymer film becomes thinner (the z-axis component contracts)as it expands in the planar directions (the x- and y-axes componentsexpand). Furthermore, the like (same) charge distributed across eachelastic film electrode causes the conductive particles embedded withinthat electrode to repel one another, thereby contributing to theexpansion of the elastic electrodes and dielectric films. Current EAParchitectures include actuators, motors, transducers, sensors, pumps,and generators. Actuators, motors and pumps are enabled by the actiondiscussed above. Generators are enabled by reversing the actiondescribed above, and sensors are enabled by virtue of changingcapacitance upon physical deformation of the material. Examples of EAPdevices and their applications are described in U.S. Pat. Nos.7,224,106; 7,211,937; 7,199,501; 7,166,953; 7,064,472; 7,062,055;7,052,594; 7,049,732; 7,034,432; 6,940,221; 6,911,764; 6,891,317;6,882,086; 6,876,135; 6,812,624; 6,809,462; 6,806,621; 6,781,284;6,768,246; 6,707,236; 6,664,718; 6,628,040; 6,586,859; 6,583,533;6,545,384; 6,543,110; 6,376,971 and 6,343,129; and U.S. Published PatentApplication Nos. 2006/0208610; 2006/0208609; 2005/0157893; and2003/0214199, the entireties of which are incorporated herein byreference.

FIGS. 3A-3D illustrate use of a subject power supply integrated withinthe flex circuit assembly 20 of FIG. 2 with a cell phone camera lensmodule 30. Module 30 includes a housing 40 which encases a lens 32 and alens positioner for adjusting the focal length of lens 32 to provideauto-focusing capability. An image sensor 42 is provided on the bottomor underside of module 30. The lens positioner includes an EAP actuatorwhich, as discussed above, is a capacitive component. The actuatorincludes electroactive film 34 held by a frame 36 which is mounted tohousing 40. Bolts 38 a and 38 b mechanically couple housing 40 to flexcircuit assembly 20 and also electrically couple the high voltage andground contacts (not shown) of the actuator to the high voltage andground leads 26 a and 26 b, respectively, of flex circuit assembly 20.While flex circuit assembly 20 in the illustrated embodiment ispositioned around the side walls of module housing 40 such that thepower components (24 a, 24 b, 24 c) face outward, assembly 20 mayalternatively be mounted to housing 40 with the power components facinginward. In the latter variation, the back or bottom side of flex circuitmay define at least a portion of the module housing structure, therebyproviding a flush exterior. With either configuration, the assigneehereof has fabricated a camera cell phone module with a power supply ofthe present invention integrated therewith having an architecture volumeno greater than about 650 mm³, weighing less than about 2 g and having apower consumption less than about 100 mW.

The present invention also provides methods associated with the subjectpower circuit for powering high-voltage devices. The methods may allcomprise the act of providing a suitable power supply, circuit, etc.Such provision may be performed by the end user. In other words, the actof “providing” merely requires the end user obtain, access, approach,position, set-up, activate, power-up or otherwise act to provide therequisite object used in the subject method.

As for other details of the present invention, such as the types ofdevices that may be powered by the subject power circuits/supplies, manysuch devices are generally known or appreciated by those with skill inthe art. The same may hold true with respect to method-based aspects ofthe invention in terms of additional acts as commonly or logicallyemployed.

The invention is not to be limited to that which is described orindicated as contemplated with respect to each variation of theinvention. Various changes may be made to the invention described andequivalents (whether recited herein or not included for the sake of somebrevity) may be substituted without departing from the true spirit andscope of the invention. Any number of the individual components,subassemblies or circuits shown may be integrated in their design. Suchchanges or others may be undertaken or guided by the principles ofdesign for assembly. In addition, where a range of values is provided,it is understood that every intervening value, between the upper andlower limit of that range and any other stated or intervening value inthat stated range is encompassed within the invention.

Also, it is contemplated that any optional feature of the inventivevariations described may be set forth and claimed independently, or incombination with any one or more of the features described herein.Reference to a singular item, includes the possibility that there areplural of the same items present. More specifically, as used herein andin the appended claims, the singular forms “a,” “an,” “said,” and “the”include plural referents unless the specifically stated otherwise. Inother words, use of the articles allow for “at least one” of the subjectitem in the description above as well as the claims below. It is furthernoted that the claims may be drafted to exclude any optional element. Assuch, this statement is intended to serve as antecedent basis for use ofsuch exclusive terminology as “solely,” “only” and the like inconnection with the recitation of claim elements, or use of a “negative”limitation. Without the use of such exclusive terminology, the term“comprising” in the claims shall allow for the inclusion of anyadditional element—irrespective of whether a given number of elementsare enumerated in the claim, or the addition of a feature could beregarded as transforming the nature of an element set forth n theclaims. Stated otherwise, unless specifically defined herein, alltechnical and scientific terms used herein are to be given as broad acommonly understood meaning as possible while maintaining claimvalidity.

In all, the breadth of the present invention is not to be limited by theexamples provided.

1. A system comprising: a high-voltage capacitive device; a powercircuit electrically coupled to the capacitive device, wherein the powercircuit is configured for stepping up a lower DC source voltage to ahigher DC output voltage, wherein the source voltage is less than about5 V, and wherein the output voltage is at least about 1.25 kV, andwherein the power circuit comprises a magnetic component and a switchingcomponent for charging and discharging the magnetic component, whereinthe switching component has a high resistance of at least about 5 ohms.2. The system of claim 1, wherein the capacitive device comprise anelectroactive polymer.
 3. The system of claim 2, wherein theelectroactive polymer forms a part of a lens positioner.
 4. The systemof claim 1, wherein the switching component has a switching frequency ofless than about 30 kHz.
 5. The system of claim 1, wherein the powercircuit defines a structure having a volume of less than about 2000 mm³.6. The system of claim 1, wherein the power circuit defines a structureweighing less than about 4 g.
 7. A system comprising: a high-voltagecapacitive device; a power circuit electrically coupled to thecapacitive device, wherein the power circuit is configured for steppingup a lower DC source voltage to a higher DC output voltage, wherein thesource voltage is less than about 5 V, and wherein the output voltage isat least about 1.25 kV, and wherein the power circuit comprises amagnetic component and a switching component for charging anddischarging the magnetic component, wherein the switching component hasa switching frequency of less than about 30 kHz.
 8. The system of claim7, wherein the capacitive device comprise an electroactive polymer. 9.The system of claim 8, wherein the electroactive polymer forms a part ofa lens positioner.
 10. The system of claim 7, wherein the power circuitdefines a structure having a volume of less than about 2000 mm³.
 11. Thesystem of claim 7, wherein the power circuit defines a structureweighing less than about 4 g.